Intercom-signal device



July 1, 1969 J. E. DURKEE ET AL 3,453,390

INTERCOM-SIGNAL DEVICE Filed Dec. 20, 1965 21m JOHN E. DUE/(E5 DUMCAA/s. REMINGTON United States Patent 3,453,390 INTERCOM-SIGNAL DEVICE JohnE. Durkee, Conesus, and Duncan S. Remington,

South Bristol, N.Y., assignors to Emerson Electric Co.,

St. Louis, Mo., a corporation of Missouri Filed Dec. 20, 1965, Ser. No.514,801 Int. Cl. H04m N00 US. Cl. 179-1 Claims ABSTRACT OF THEDISCLOSURE A combined intercom and door chime especially adapted forattachment to an existing door chime in, stallation. A remote stationcontaining a speaker/microphone and a chime button connected in parallelwith the speaker/microphone replaces the original door chime button. Acentral station having a second speaker/microphone and a function switchis positioned at a central location. The function switch is biased to aposition in which the chime button is connected in series to a chimecircuit relay and a direct current source. Depression of the chimebutton closes this circuit and thereby causes the relay to close an ACchime circuit and activate the chime solenoid. Two other positions ofthe function switch connect the speaker/microphones to an amplifier andsimultaneously connect the direct current source to the amplifier.

This invention relates to communication systems. It has particularapplication to intercom systems with one speaker/microphone locatedinside a dwelling and another speaker/microphone, associated with a doorchime, at an outside door of the dwelling, but is not limited thereto.

Conventional door chime systems consist of a chime button, a 16-volttransformer, and a chime which, electrically, is essentially a chimesolenoid. Two electrical wires lead from the chime button location tothe transformer. Two other electrical wires lead from the chime solenoidto the transformer. One of the chime button wires is connected to theground side of the transformer. The other chime button wire is connectedto one side of the chime solenoid. The other side of the chime solenoidis connected to the hot side of the transformer.

Presently known door chime-intercom devices have an outdoor station witha speaker/microphone and a chime button, an indoor speaker/microphone,an amplifier, a transformer, and a chime. Two wires lead from theoutdoor speaker/microphone to the indoor speaker/microphone. Twodilferent wires lead from the chime button to the transformer and arewired in the conventional door chime manner just described. Thus, anoutdoor station with both a speaker/microphone and a chime buttonpresently requires four electrical wires leading to interior locations.

The installation of a doorbell-intercom system in a home which alreadyhas a door chime system is thus difficult. Not only must an outdoor andan indoor station be installed and a power cable led from the indoorstation to the transformer, but new wires must be led from the outdoorstation to either the transformer or the indoor station. Installingthese wires requires either making new openings through the outer wallor fishing the wires through existing wireways.

One of the objects of this invention is to providea chime-intercomsystem device which is easier to install than devices known heretofore.

Another object is to provide such a device which is inexpensive tomanufacture and maintain.

Still another object is to provide such a device in which the intercomsystem is controlled entirely from a location remote from the chimebutton.

Other objects will become apparent to those skilled in the art in thelight of the following description and accompanying drawings.

In accordance with this invention, generally stated, an intercom-signaldevice is provided including a remote station which has only twoelectrical leads, and uses these same two leads for both a signallingfunction and an intercom function.

The remote station houses a signal switch (chime button), which is partof a signal switch circuit, and a remote speaker, which is part of anintercom circuit. The switch and speaker are connected in parallel tothe two leads. As used hereinafter, the term speaker means aspeaker/microphone. The signal switch circuit is a control circuit foran AC signal circuit; the signal switch circuit itself carries directcurrent. This direct current is blocked from the remote speaker by meanswhich in the preferred embodiment takes the form of a capacitor in theintercom circuit. The intercom circuit carries alternating audiofrequency current when the remote speaker is in use. This current ispassed by the capacitor. Because the signal switch is normally biasedopen, the signal switch circuit does not normally short across theintercom circuit, although it does so when the signal switch is closedmanually against the bias, by-passing the remote speaker. Thus, thesignal switch circuit and the intercom circuit, although connected inparallel to the same two leads, effectively operate independently.

One of the two wires from the remote station leads to a three-way switchwhich connects it selectively to a DC power supply through a signalcircuit relay, to the input of an amplifier, or to the output of anamplifier. The other wire is grounded.

In the illustrative embodiment described, the function switch, signalcircuit relay, amplifier, and -a second speaker are all located at anindoor station, and the signal (a door chime) and the transformer fromwhich the system is powered are at different locations. For someapplications, the grouping of these elements could be altered. However,the configuration of elements described in the illustrative embodimentis advantageous.

In the illustrative embodiment, a door chime-intercom device is providedwhich utilizes all of the wiring of a pre-existing standard l6-volt doorchime system, which requires the removal of only the door chime button,and which requires the addition of only an outdoor station, an indoorstation and a single S-Wire cable from the indoor station to a junctionpoint, generally at the transformer location.

In the drawing, FIGURE 1 is a somewhat diagrammatic front plan view ofthe main elements of one illustrative embodiment of the device of thisinvention; and

FIGURE 2 is a diagrammatic representation of the illustrative circuitdescribed.

Referring now to the drawing for one illustrative embodiment of thisinvention, reference numeral 1 indicates an intercom-signal device ofthis invention, which, in the illustrative embodiment shown in FIGURE 1includes an inside speaker station 2, an outside speaker station 3, achime housing 5, and a transformer station 6.

The inside speaker station includes a standard amplifier 4, a speaker 8,a function switch control 9, a volume control 7, and electricalconnections for a five-wire cable 10 containing electrical conductors11, 12, 13, 14 and 15. The conductor 12 constitutes a common ground. Theoutside speaker station 3 includes a chime button 17, a speaker 18, andelectrical connections for wires 11 and 12. The chime housing 5 containsa chime of the standard type in which activation of a solenoid 19 causesthe chime to sound. The transformer station 6 includes a transformer 20with terminals 21 and 22 connected to two ends of a secondary coil 23,and terminals 24 and 25 connected to two ends of a primary coil 26 andto a source of AC current (house current) not here shown. The terminal21 is connected to the common ground 12. The terminal 22 is connected toelectrical conductor 14. The lectrical conductor 14 is connected torectifier 150, of conventional configuration, which includes a resistor35, a diode 36 and a capacitor 37. The output side of the rectifier 150is electrically connected to a movable arm 65 of a switch 60. The switch60 is one of three switches 60, 70 and 80, mechanically linked, whichmake up a function switch 90. The function switch 90 is a three-positionswitch.

Thus, the three switches 60, 70 and 80 have a middle contact 62, 72 and82 respectively, to which the switch is normally biased, an upper, talkcontact 61, 71 and 81 respectively and a lower, listen contact 63, 73and 83 respectively. The function switch can be turned manuallyselectively to the talk or listen position from the inside speakerstation, returning to the middle or standby position when released.

In the illustrative specific embodiment of a suitable electricalcircuit, shown in FIGURE 2, the transformer 20 is a standard l6-voltchime transformer which supplies power to a chime circuit and, through arectifier, to a chime control circuit and an intercom circuit.

The chime circuit is connected to the electrical conductor 14 from theterminal 22 of the transformer 20 by means of electrical conductor 16.Conductor 16 is connected to one side of the chime solenoid 19. Theother side of chime solenoid 19 is connected, by electrical conductor toone stationary contact 31 of a relay 30. The relay 30 also includes arelay solenoid 32, a movable switch arm 33 and a fixed contact 34. Theswitch arm 33 is electrically connected to the ground wire 12. Whenrelay solenoid 32 is activated (by completion of a chime controlcircuit) switch arm 33 is brought into contact with contact 31 andcompletes the chime circuit.

The chime control circuit is connected to a fixed normal positioncontact 62 of the switch 60.

When function switch 90 is in a middle position, switch arm 65 is inelectrical contact with fixed terminal 62, hence the chime ringingcircuit is electrically connected to the rectifier 150. Terminal 62 isconnected by an electrical conductor 38 to a terminal 39. Terminal 39 isconnected to a large resistor 40 which is connected to the stationarycontact 34 of relay 30. Resistor 40 functions as a voltage divider. Whenrelay solenoid 32 is not activated, contact 34 is grounded throughswitch arm 33 and ground wire 12. Terminal 39 is also connected to oneside of relay solenoid 32. The other side of relay solenoid 32, isconnected by an electrical conductor 41 to a contact 72 of switch 70.When the function switch 90 is in its middle position, contact 72 isconnected by a switch arm 75 to electrical conductor 11. Conductor 11 isconnected to a terminal 42, in the outside speaker station 3. Terminal42 is connected by an electrical conductor 46 to a contact 44 of a chimeswitch 47. The other terminal 45 of chime switch 47 is connected byelectrical conductor 48 to a terminal 43. Terminal 42 is alsoelectrically connected to terminal 43 through a parallel circuitconsisting of an electrical conductor 49, a speaker 18, an electricalconductor 50, a nonpolarized capacitor 51, and an electrical conductor52 attached to terminal 43. As will be explained hereinafter, thisparallel circuit is not a part of the chime control circuit. Terminal 43is connected to the common ground wire 12.

The intercom circuit is completed when function switch 90 is in eitherthe upper or lower position. When the function switch 90 is in the upperposition, switch arm 65 is in contact with contact .61, switch arm 75with contact 71, and switch arm 85 with contact 81. When the functionswitch 90 is in the lower position, switch arm 65 is in contact withcontact 63, switch arm 75 with contact 73, and switch arm 85 withcontact 83. As can be seen in FIGURE 2, contacts 61 and 63 are bothelectrically connected to a power terminal 91 of the amplifier 4.Contacts 71 and 83 are both electrically connected to an output terminal92 of the amplifier 4. Contacts 73 and 81 are both electricallyconnected to an input terminal 93 of the amplifier 4. When the functionswitch 90 is in the upper position, amplifier power terminal 91 isconnected to rectifier 150. Amplifier output terminal 92 is electricallyconnected through switch arm and electrical conductor 11 to terminal 42in the outside station 3. Terminal 42 is connected through the outsidespeaker 18 and nonpolarized capacitor 51 to terminal 43 and the groundas hereinbefore described. Amplifier input terminal 93 is electricallyconnected through switch arm and electrical conductor 53 to the insidespeaker 8. The speaker 8 is also connected by an electrical conductor 54to the common ground 12. When the function switch is in its lowerposition, switch arm 75 is connected to amplifier input terminal 93 andswitch arm 85 is electrically connected to amplifier output terminal 92through contact 85. The circuits are otherwise the same.

The non-polarized capacitor 51 consists of two capacitors back-to-back.Its function is to block non-pulsed direct current. Thus, the DC of thechime control circuit is blocked by the capacitor 51, but thealternating audio frequency current of the amplifier output or input ofthe intercom system is passed. The non-polarized capacitor 51 also makesunimportant whether electrical conductors 11 and 12 are connected toterminals 42 and 43 or terminals 43 and 42 respectively.

Merely by way of illustration, and not by way of limitation, componentsof the following values or character may be used in the illustrativecircuit described and illustrated:

farads, 64 v.

Although the construction of the amplifier forms no part of thisinvention, it may be noted that components of the following characterand values are well suited for use in the amplifier of the illustrativeembodiment:

Reference numeral: Value or description 101 Capacitor, 125 microfarads.

102 Capacitor, 0.47 microfarad.

103 Capacitor, 0.10 microfarad.

104 Capacitor, 0.22 microfarad.

105 Capacitor, 250 microfarads.

106 Capacitor, 0.0015 microfarad. 107 Resistor, 390 ohms.

108 Resistor, variable, 500 ohms.

109 Resistor, 10K ohms.

110 Resistor, 100K ohms.

111 Resistor, 47 ohms.

112 Resistor, 10K ohms.

113 Amplifier, typically GE 2N 2923. 114 Amplifier, typically GE 2N2924. 115 Amplifier, typically GE 2N 2923. 116 Output transformer.

The illustrative device operates as follows: Chime switch 47 is normallybiased open. Function switch 90 is normally biased to the middleposition. Relay switch 33 is normally biased into contact with terminal34. Therefore, the only normal current flow is a very small directcurrent from the rectifier through contact 62 of switch 60, electricalconductor 38, resistor 40, terminal 34, and switch arm 33 to the ground.Resistor 40 has a high resistance, so that the current flow is small.

When chime button 17 is depressed, chime switch 47 is closed, and thechime control circuit is completed. Direct current flows from therectifier 150' through the relay solenoid 32, through conductor 11,through the chime switch 47, and through conductor 12 to the ground.Energization of the relay solenoid 32 throws relay switch arm 33,completes the (AC) chime circuit through the chime solenoid 19, andsounds a chime. When chime button 17 is released, all circuits return totheir normal states.

The intercom functions of the illustrative device are entirelycontrolled from the inside speaker station. Turning the function switchcontrol 9 to a talk position moves the function switch 90 to its upperposition. The inside speaker 8 is then connected to the amplifier inputterminal 93 and acts as a microphone. Sounds picked up by the insidespeaker 8 are emitted at amplifier output terminal 92 as amplifiedalternating audio frequency current. The outside speaker 18 is connectedto the amplifier output terminal 92 by electrical conductor 11 and actsas a speaker. The non-polarized capacitor 51 will pass the alternatingaudio frequency amplifier output; therefore, the outside speaker circuitis completed through line 12 to the ground.

When the function switch control is turned to a listen position, thefunction switch 90 is moved to its lower position. The outside speaker18 is then connected through conductor 11 to the amplifier inputterminal 93 and acts as a microphone. The outside speaker circuit isagain grounded through conductor 12 because the non-polarized capacitor51 passes the alternating audio frequency current. The inside speaker 8is connected to the amplifier output terminal 92.

It will be apparent that when the function switch control is in itsnormal position neither speaker is activated and the chime can besounded. When the function switch control 9 is turned to either the talkor listen position, the chime control circuit is broken and depressionof the chime button 17 will not sound the chime.

The installation of the device described, to replace a standard doorchime system, is extremely simple. The existing door chime button isremoved and its wires are attached to terminals 42 and 43 of the outsidestation 3. The outside station 3 is then attached to the outdoor wall.The five-wire cable is led from the transformer station to the insidespeaker station location, and each of the five wires 11-15 is attachedto a corresponding wire of the inside speaker station. The insidespeaker station is attached to an indoor wall. At the transformerstation, the two wires from the outside speaker station are disconnectedfrom transformer terminal 21 and from a chime wire, and attached towires 11 and 12 of the five-wire cable. The loose chime wire is attachedto wire 15. The other chime wire is already attached to transformerterminal 22 and is not disturbed. Wire 14 is attached to transformerterminal 22. Wire 13 is attached to transformer terminal 21. The deviceis then in operating condition. If there is another door chime circuitfor another door attached to the transformer and chime, it need not betouched at all. The two circuits will continue to operate independently.

Numerous variations in the construction of the various components of thedevice of this invention, within the scope of the appended claims, willoccur to those skilled in the art. For example, any number of speakers,either in the broad sense or in the limited sense of speakers withoutmicrophones, can be connected to the system. Radio receivers can beconnected to play over the various speakers. Various of the elements ofthe system may be located in other positions or housed diiferently fromthe arrangement shown. The system may be used entirely inside, as afactory communication system, for example. These are merely illustrativevariations.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. An intercom-signal device comprising a remote station including aspeaker and a signal switch; two electrical conductors electricallyconnected to said speaker in at least one position of said signalswitch, said signal switch selectively electrically connecting one ofsaid conductors with the other of said conductors, and switch meanselectrically connected to one of said conductors for selectivelyconnecting said conductor to a direct current source at one position ofsaid switch means and to an amplifier at another position of said switchmeans. 2. The intercom-signal device of claim 1, in which said signalswitch is connected electrically in parallel with said speaker andincluding blocking means connected electrically in series with aconductor electrically connected to said speaker for blocking directcurrent.

3. The intercom-signal device of claim 2 in which the blocking meanscomprise a non-polarized capacitor.

4. An intercom-signal device comprising an AC signal circuit, a DCsignal control circuit, including a signal switch, for selectivelyenergizing and de-energizing said AC signal circuit, and an intercomcircuit comprising a first and a second speaker, said first speakerbeing connected electrically in parallel with said signal switch.

5. The intercom-signal device of claim 4 including function switch meansfor selectively connecting said signal switch to said signal controlcircuit and said first speaker to said intercom circuit, said firstspeaker and said signal switch being located in a remote location andsaid second speaker and said function switch means being located in acentral location.

6. The intercom-signal device of claim 4 in which blocking means areconnected electrically in series with said first speaker to blocknon-pulsed direct current through said speaker.

7. The device of claim 6 in which the blocking means comprise anon-polarized capacitor.

8. An intercom-signal device comprising first and second speakerspositioned remotely from one another; an amplifier selectivelyconnectable to both said speakers; a source of direct currentselectively connectable to said amplifier; a first electrical conductorat least normally electrically connected with the first speaker andselectively connectable with said direct current source and saidamplifier; a second electrical conductor at least normally connected tosaid first speaker and to ground; direct current blocking means inseries with one of said first and second electrical conductors; a signalcontrol circuit, and switch means, in said signal control circuit,selectively connecting said first and second electrical conductors.

9. In an intercom-signal device having at least two speakers, anamplifier electrically connectable to said speakers, an electricallyoperated chime and a chime switch, the improvement comprising twoelectrical conductors at least normally connected to a first of saidspeakers, one of said conductors being electrically connected to ground,the second of said conductors being electrically connected to a controlswitch; a blocking capacitor connected electrically in series with oneof said electrical conductors; a direct current source; a chime circuitincluding said chime; a chime transformer electrically connected to theinput side of said direct current source and to said chime circuit; achime circuit switch in said chime circuit; a solenoid connected tooperate said chime circuit switch, said control switch electricallyconnecting, in a first of its operative positions, said second of saidelectrical conductors to said solenoid and the output side of saiddirect current source electrically in series,

said control switch electrically connecting, in a second of itsoperative positions, said second of said electrical conductors to theinput side of said amplifier,

said control switch electrically connecting, in a third of its operativepositions, said second of said electrical conductors to the output sideof said amplifier, said control switch normally being biased to saidfirst operative position,

said chime switch in one of its operative positions electricallyconnecting said first and second conductors between said first speakerand said solenoid, said chime switch normally being biased out of saidone operative position,

whereby moving said chime switch to said one operative position whensaid control switch is in its normally biased position completes acircuit from said direct current source through said solenoid and saidchime switch to ground.

10. An intercom-signal device comprising a first station including afirst speaker and a signal switch; a second station including a secondspeaker and a function switch; exactly two electrical conductors leadingout of said first electrical conductors to each other in one of itsoperative positions; and an amplifier having an input side and an outputside; said function switch selectively electrically connecting one ofsaid conductors to said input side of said amplifier in one of itsoperative positions and to said output side of said amplifier in asecond of its operative positions.

References Cited UNITED STATES PATENTS KATHLEEN H. CLAFFY, PrimaryExaminer.

station, said signal switch electrically connecting said 15 C. W.JIRAUCH, Assistant Examiner.

